A day of grace and rest from work
In respecting religious liberty and the common good of all, Christians should seek recognition of Sundays and the Church's holy days as legal holidays. They have to give everyone a public example of prayer, respect, and joy and defend their traditions as a precious contribution to the spiritual life of society. If a country's legislation or other reasons require work on Sunday, the day should nevertheless be lived as the day of our deliverance which lets us share in this "festal gathering," this "assembly of the firstborn who are enrolled in heaven."
Source: Catechism of the Catholic Church (Vatican.va)